Siding is a common building covering, frequently used in wood-framed buildings to protect against water. Over time, ordinary weathering and other damage may degrade the integrity of building siding, which may then require repair or replacement. Insurers may photograph damaged building siding to make a record of its condition for claims adjustment and repairs. It is also possible to use measurements of lengths of portions of the building siding derived from an image to determine size of the building siding. For example, the methods described in Mauer et al., U.S. Pat. No. 8,885,916, may be used to identify a siding product using measurements derived from an image. Such measurements require a reference object of known length within the image. Additionally, because siding is typically installed upon the exterior of buildings, lighting conditions in which such photographs are captured can vary substantially over the course of seasons, days, or hours. This has been considered acceptable because the photographs had previously been used for reference only, and human adjusters attempt to take into consideration such changes in lighting conditions when reviewing the photographs. Such variation in lighting, exposure, and camera characteristics would be problematic if automatic processing were applied to such images, however.
In an unrelated field, color charts are used by professionals in entertainment, advertising, photography, and fine art industries. Color charts provide a set of known color patches for comparison against observed colors. Color charts frequently also provide scales of known length and dimensions for reference of distances within the image. In addition to determine size measurements of objects in captured images, color charts are typically used to check color calibration in reproductions of images or to allow a photographer to adjust camera settings prior to image capture, which may include adjusting parameters to obtain a desired color temperature and white balance. In order to use color charts for measuring objects or determining colors within an image, however, the color chart must be photographed with the image. This is typically performed by holding the color chart near an object of interest when the image is captured. This method may require an additional person to hold the color chart, however, which may further interfere with lighting conditions (e.g., by blocking light sources or by reflection).